This rotating knife is the cutting element on the straw chopper drum of a forage harvester. It mounts on the drum and interacts with a stationary counter-knife to shear crop material into short lengths. The knife rotates with the drum, and its 3 mm thickness determines the cutting gap that affects chop quality. A worn or dull knife increases the cutting gap, producing longer, unevenly cut material and placing higher load on the drive system. The knife is secured with matching bushings, one external and one internal, which align it on the mounting stud. When replacing, install the bushings in the correct order and tighten the retaining nut to specification.